package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.Objects;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    @Resource
    private CacheClient cacheClient;


    @Override
    public Result queryById(Long id) {
        //缓存穿透
//        Shop shop = queryWithPassThrough(id);
        
        //互斥锁解决缓存穿透
//        Shop shop = queryWithMutex(id);
//
//        if (shop == null){
//            return Result.fail("店铺不存在");
//        }

        //逻辑过期解决
//        Shop shop = queryWithLogicalExpire(id);

//        Shop shop = cacheClient.queryWithPassThrough(
//                RedisConstants.CACHE_SHOP_KEY,
//                id,
//                Shop.class,
//                this::getById,
//                RedisConstants.CACHE_SHOP_TTL,
//                TimeUnit.MINUTES);

        Shop shop = cacheClient.queryWithLogicalExpire(
                RedisConstants.CACHE_SHOP_KEY,
                id,
                Shop.class,
                this::getById,
                RedisConstants.CACHE_SHOP_TTL,
                TimeUnit.MINUTES);

        if (shop == null){
            return Result.fail("店铺不存在");
        }

        return Result.ok(shop);
    }

    public Shop queryWithPassThrough(Long id) {
        String key = RedisConstants.CACHE_SHOP_KEY + id;
        //1、从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2、判断是否存在
        if (StrUtil.isNotBlank(shopJson)){
            //3、存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        if (Objects.equals(shopJson, "")){
            return null;
        }

        //4、不存在，根据id查询数据库
        Shop shop = getById(id);

        //5、数据库中不存在，返回错误
        if (shop == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(
                    key,
                    "",
                    RedisConstants.CACHE_NULL_TTL,
                    TimeUnit.MINUTES);

            return null;
        }

        //6、存在，写入redis
        stringRedisTemplate.opsForValue().set(
                key,
                JSONUtil.toJsonStr(shop),
                RedisConstants.CACHE_SHOP_TTL,
                TimeUnit.MINUTES);
        return shop;
    }

    private Shop queryWithMutex(Long id) {
        //1、从redis查询商铺缓存
        String key = RedisConstants.CACHE_SHOP_KEY + id;
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        Shop shop;

        //2、判断是否存在
        if (StrUtil.isNotBlank(shopJson)){
            //3、存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        if (Objects.equals(shopJson, "")){
            return null;
        }

        //4、实现缓存重建
        //4.1 获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        try {

            //4.2 判断是否获取成功
            while (!isLock){
                //4.3 失败，则休眠并重试
                Thread.sleep(50);
                isLock = tryLock(lockKey);
            }

            //不存在，根据id查询数据库
            shop = getById(id);

            //5、数据库中不存在，返回错误
            if (shop == null){
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(
                        key,
                        "",
                        RedisConstants.CACHE_NULL_TTL,
                        TimeUnit.MINUTES);

                return null;
            }

            //6、存在，写入redis
            stringRedisTemplate.opsForValue().set(
                    key,
                    JSONUtil.toJsonStr(shop),
                    RedisConstants.CACHE_SHOP_TTL,
                    TimeUnit.MINUTES);

        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }

        return shop;
    }

    private Shop queryWithLogicalExpire(Long id) {
        //1、从redis查询商铺缓存
        String key = RedisConstants.CACHE_SHOP_KEY + id;
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2、判断是否存在
        if (StrUtil.isBlank(shopJson)){
            //3、存在，直接返回
            return null;
        }

        //4、命中，需要先把json反序列化成对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();

        //5、判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())){
            //5.1、未过期，直接返回店铺
            return shop;
        }

        //5.2、过期，需要缓存重建
        //6、缓存重建
        //6.1、获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2、判断是否获取成功
        if (isLock){

            shopJson = stringRedisTemplate.opsForValue().get(key);
            redisData = JSONUtil.toBean(shopJson, RedisData.class);
            expireTime = redisData.getExpireTime();

            if (expireTime.isAfter(LocalDateTime.now())){
                //6.2.1、未过期，直接返回店铺
                return shop;
            }

            //6.3、成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                //重建缓存
                try {
                    this.saveShop2Redis(id, 20L);
                }catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    unlock(lockKey);
                }
            });
        }
        //6.4、返回过期的店铺信息
        return shop;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

    public void saveShop2Redis(Long id, Long expireSeconds){
        //1、查询店铺信息
        Shop shop = getById(id);
        //2、封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3、写入redis
        stringRedisTemplate.opsForValue().set(RedisConstants.CACHE_SHOP_KEY+id, JSONUtil.toJsonStr(redisData));
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null){
            return Result.fail("店铺id不能为空");
        }
        //1、更新数据库
        updateById(shop);

        //2、删除缓存
        stringRedisTemplate.delete(RedisConstants.CACHE_SHOP_KEY + id);

        return Result.ok();
    }
}
